An open plea to Joy Christian and Fred (and maybe others) to get the facts straight re CHSH - http://users.unimi.it/aqm/wp-content/uploads/CHSH.pdf. For your current position re CHSH (see your posts hereunder), weakens any other claim that you make in the contested area of local-realism.

NB: I am a determined local-realist so, in some places below, where the definition of "local-realism" needs to be clarified, I will add a "[sic]". But, please note, the CHSH inequality is unaffected by such sic-ing.

Joy Christian wrote:Gordon Watson wrote:Fred, I'm not sure what you are getting at here. I'd welcome some elaboration, especially re this: "they use the same trickery as usual to show a "violation" of Bell-CHSH." Doesn't QM theory and practice violate Bell-CHSH? Thanks.

Gordon,

Nothing can violate a mathematical inequality. It is insane even to suggest that something can "violate" a mathematical inequality.

So, no. Neither quantum mechanics nor any experiment violates Bell-CHSH inequality. How can they?

It seems that in this forum only Michel, Fred, and I understand this.

To be sure, quantum mechanics makes a different prediction (as does my local model) for the Bell-CHSH string of expectation values; namely, CHSH < 2\/2 (not 2).

But that is not the same thing as claiming that quantum mechanics "violates" CHSH < 2. It simply means that CHSH < 2 is just wrong.

I will let Fred elaborate on the trickery of how experimentalists switch to CHSH < 4 in practice. Although Michel has explained this dozens of times in this forum.

Joy

FrediFizzx wrote:Joy Christian wrote: I will let Fred elaborate on the trickery of how experimentalists switch to CHSH < 4 in practice. Although Michel has explained this dozens of times in this forum.

Let me qualify that an inequality of Bell's type is mathematically impossible to violate. That is just the trickery; they shift to a different inequality where the bound is 4 for CHSH. In Bell-CHSH, the expectation terms are dependent on elements in each other so you have a bound of 2. For QM and the experiments, the expectation terms are independent thus by simple mathematical inspection one can have,

+1 -(-1) +1 +1 = 4

Dear Joy and Fred,

Fact 1: From their Abstract, here's what CHSH - http://users.unimi.it/aqm/wp-content/uploads/CHSH.pdf - did (with my emphasis).

- "A theorem of Bell, proving that certain predictions of QM are inconsistent with the entire family [sic] of local hidden-variable theories, is generalized so as to apply to realizable experiments. A proposed extension … polarisation correlation … will provide a decisive test between QM and local hidden-variable theories [sic]."

Fact 2: The usual form of the CHSH inequality (eg, https://en.wikipedia.org/wiki/CHSH_inequality) is:

|E(a, b) - E(a, b') + E(a', b) + E(a', b')| ≤ 2; (1)

where a and a′ are detector settings on Alice's side, b and b′ on Bob's side B.

Fact 3: It is not essential but some might like to add "the four combinations may be tested in separate sub-experiments".

Fact 4: The terms in LHS (1) are unqualified: so they apply - without restriction - to relevant theories and relevant realisable experiments.

Fact 5: Experiments (eg, by Aspect, with photons pairwise correlated in a singlet state), have breached (1).

HTH, Gordon

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